Google Closure, Response Always Empty - php

Question

I'm trying to get together a basic example of how to use Google Closure to minify JS. I can't seem to get this to work at all.
I'm trying to follow these examples:
https://developers.google.com/closure/compiler/docs/gettingstarted_api
http://closure-compiler.appspot.com/home
When working on API's and/or AJAX code, the first thing I try to is get the variables and values setup properly using just Advanced Rest Client Applications - a Chrome Extension. Whenever I send this data, though, I get an empty response (image below).
Trying to insert the same code into my PHP code, no matter what I send in the $postData variable, I get an empty (null) response.
PHP Code:
$postData =
http_build_query(
[
'output_info' => 'compiled_code',
'output_format' => 'text',
'compilation_level' => 'SIMPLE_OPTIMIZATIONS',
'js_code' => urlencode("function hello(name) { // Greets the user alert('Hello, ' + name); } hello('New user');")
]
);
$ret = $this->ci->curl->simple_post(
$url,
$postData,
$options
);
var_dump($ret);
die();
Response:
string ' ' (length=1)
I'm 99% confident that I'm missing something to use the Closure API like a key or something, but I have no idea how to proceed.

Answer 1

After many, many, many attempts, I found that if I used rawurlencode() instead of urlencode(), it works. Here's the final function.
// use google closure to get compiled JS
$encoded = rawurlencode($js);
$postData =
'output_info=compiled_code&' .
'output_format=text&' .
'compilation_level=WHITESPACE_ONLY&' .
'js_code=' . $encoded
;
$options = [];
$call = curl_init();
curl_setopt_array(
$call,
array(
CURLOPT_URL => 'http://closure-compiler.appspot.com/compile',
CURLOPT_POST => 1,
CURLOPT_POSTFIELDS => $postData,
CURLOPT_RETURNTRANSFER => 1,
CURLOPT_HEADER => 0,
CURLOPT_FOLLOWLOCATION => 0
)
);
$jscomp = curl_exec($call);
return $jscomp;